1. Field of the Invention
The present invention relates to a camera having a vibration correcting device for correcting an image blur caused concomitantly with a camera shake or the like and a vibration correcting device incorporating a zoom photographic optical system.
2. Related Background Art
In a type of conventional camera having a vibration correcting device, as compared with a camera not having a vibration correcting device, a breakoff time of the shutter operation can be made closer to a slow shutter side by dint of action of the vibration correcting device. In a camera switchable over to a flashlight emitting mode and a flashlight inhibition mode, however, the breakoff time exists in each mode. But, there is no camera which deals with the breakoff time of the shutter operation in relation to both modes.
In the case of flashlight photographing, a flash duration of the electronic flash is short, and, hence, there is no problem in terms of a camera shake with respect to a principal object. When photographed by a considerably slow shutter, however, there arises a problem in which the background is blurred. Particularly when a comparatively strong camera shake is caused in a state where a partially bright portion exists on the background, there is produced such a problem that the light is superposed on the principal object, resulting in a photo which is hard to see.
Further, in a recent camera, the respective mechanisms such as an auto exposure (AE) mechanism, an autofocus (AF) mechanism, etc., are electronized and highly automated. One of such higher functions is a function to correct a vibration derived from the camera shake in the photographing of an object when holding the camera with hands, and a variety of functions are proposed.
By the way, the problem induced when correcting such an image blur is that a necessary vibration correcting accuracy probably can not be probably obtained depending on a photographing condition.
That is, in the conventionally known camera having the vibration correcting device, the simplest way of correcting the vibration due to the camera shake or the like is to click the shutter at a speed higher than a shutter speed substantially determined by an inverse number of a focal length of a photographing lens. It has been considered that the camera shake is thus prevented.
The above-mentioned conventional camera, however, causes inconveniences in the following cases and brings about a problem in which the necessary exposure photographing can not be adequately effected.
That is, when trying to take a photo by a telephoto lens, and if, for example, the focal length is 120 mm, the shutter has to be pressed at a shutter speed higher than approximately 1/125 sec. The problem is that the photographing is impossible when getting dark.
Further, when performing the flashlight photographing, the flash duration of the electronic flash is short, and, therefore, there is no problem in terms of the camera shake with respect to the principal object. However, when photographed by the comparatively slow shutter, there exists the problem in which the background is blurred.
Especially when the relatively strong vibration is caused in the state where the partially bright portion exists on the background, the light is superposed on the principal object, resulting in the hard-to-see photo. For this reason, the arrangement is such that the shutter speed is not slower than the shutter speed in the vicinity of the above-stated inverse number of the focal length in the case of the flashlight photographing, too.
Namely, the problem inherent in the conventional camera is that it is impossible to take a proper photo including the background when photographed in a dark place. There exists a necessity for taking some measures to compensate.
Also, when photographing by use of a flashlight device, it can not be said that the photographing operation making full use of the background light takes place. Further, in a slow synchro mode, it is also impossible to take a natural photo which makes the most of the background, and such a point has to be taken into consideration.
Particularly, it is required that this type of camera be constructed to exhibit effects of the vibration correcting device even when photographing in a dark place. Furthermore, in the camera using a zoom lens, the photo has to be taken while effecting the zooming. It is desired that some measures for obviating the above problems are to be taken in view of these points.
Additionally, Japanese Patent Application Laid-Open No. 2-11683 discloses one of the conventional vibration correcting devices. The vibration correcting camera disclosed therein is constructed such that external light photographing is selected when making a determination of falling within a vibration correcting range, while the flashlight photographing is automatically selected when making a determination of being beyond the vibration correcting range.
In the above vibration correcting camera, a drive time TA of a vibration correctable limit shutter is predetermined. In a comparison of the above drive time TA with TV obtained from a result of a light measurement, if TV.ltoreq.TA, the external light photographing is selected. If TA.gtoreq.TV, there is made the determination of being beyond the vibration correcting range, and the flashlight photographing in a specified shutter drive time is to be selected. In this case, the vibration correcting device is not allowed to function in the flashlight photographing. Furthermore, in the case of a distance which is so long that a flashlight does not reach that distance when TV.gtoreq.TA, the flashlight is not emitted, and, instead, the external light photographing is carried out. In this case also, the vibration correcting device is not allowed to function in the same way as with the above flashlight photographing.
Given, however, are the following problems inherent in the above-described conventional vibration correcting camera.
In the case of distant-view photographing wherein the flashlight is not reached, the vibration correcting device does not work, and hence there is a possibility in which a blurred photo is to be taken. Besides, in the case of the flashlight photographing, the vibration correction control is not performed, and, therefore, the shutter drive time is generally set to 1/60 sec. as a measure for preventing the blurred photo. For this reason, it happens that an unnatural photo is taken with an underexposure of the background.